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MathGroup Archive 2003

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Re: Handling expressions. Could any one find a more direct way?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg39921] Re: Handling expressions. Could any one find a more direct way?
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Wed, 12 Mar 2003 02:28:00 -0500 (EST)
  • Organization: Universitaet Leipzig
  • References: <b4k3og$8fl$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

Solve[0 == # & /@ CoefficientList[Numerator[Together[A - b]], s],
  {k10, k21, k12, k13, k31}]

Regards
  Jens

Guillermo Sanchez wrote:
> 
> (*A need to obtain   {k10, k21, k12, k13, k31}  knowing that A = b
> where*)
> 
> A = 0.1/(0.1 + s) + 0.2/(1 + s) + 0.7/(5 + s);
> 
> b = (k21*k31 + k21*s + k31*s + s^2)/(k10*k21*k31 + k10*k21*s +
> k13*k21*s +
>      k10*k31*s + k12*k31*s + k21*k31*s + k10*s^2 + k12*s^2 + k13*s^2 +
>      k21*s^2 + k31*s^2 + s^3);
> 
> (*Here is my procedure*)
> 
> A1 = Together[ExpandAll[Factor[A]]]
> 
> n1 = Numerator[A1]
> 
> d1 = Denominator[A1]
> 
> n2 = Collect[Numerator[b], s]
> 
> d2 = Collect[Denominator[b], s]
> 
> (*Now, handing the solution for previous output -they are been
> eliminated in this mail- I can obtain  {k10, k21, k12, k13, k31}*)
> 
> Solve[{k21*k31== 0.67, 2.39 == k21 + k31, k10*k21*k31 == 0.5,
>    k10*k21 + k13*k21 + k10*k31 + k12*k31 + k21*k31 == 5.6,
>    k10 + k12 + k13 + k21 + k31 == 6.1}, {k10, k21, k12, k13, k31}]
> 
>   (* Could any one find a more direct way?*)
> 
>   Guillermo Sanchez


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